1.) Untouchable - important because of low agility.2.) Implacable - you should be able to hit with those few attacks you have. 3.) Armor - A lot of health is not enough without this one.4.) Master of Arms - Melee weapons like sai or knife do hit often even if the opponent has high agility. Damage bonus comes in handy here.

In fact, I'd never keep an immortal brute, not even Piston-naga or Fotum, but that's just me.

They are great in the beginning which I consider <100 level, but higher level they get, less they are able to compensate for the stat loss.